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You are here: Home / Data and maps / Indicators / Nutrients in transitional, coastal and marine waters / Nutrients in transitional, coastal and marine waters (CSI 021) - Assessment published Nov 2005

Nutrients in transitional, coastal and marine waters (CSI 021) - Assessment published Nov 2005

Topics: , ,

Generic metadata

Topics:

Water Water (Primary topic)

Coasts and seas Coasts and seas

Tags:
atlantic ocean | csi | nitrates | north sea | mediterranean | water | phosphates | baltic region | coastal ecosystems
DPSIR: State
Typology: Descriptive indicator (Type A - What is happening to the environment and to humans?)
Indicator codes
  • CSI 021
 
Contents
 

Key policy question: Are nutrient concentrations in our surface waters decreasing?

Key messages

Phosphate concentrations in some coastal sea areas of the Baltic and North Seas have decreased over recent years, but they have remained stable in the Celtic Sea and increased in some Italian coastal areas.  Nitrate concentrations have generally remained stable over recent years in the Baltic, North and Celtic Seas but have increased in some Italian coastal areas.

Mean winter surface concentrations of phosphate in the Greater North Sea, the Celtic Seas and the Northeast Atlantic, 2003

Note: Coastal stations are marked by circles and ICES open-water stations (>20 km from coast) by squares

Data source:

Waterbase (data from OSPAR, HELCOM and EEA member countries compiled by ETC Water).

Downloads and more info

Mean winter surface concentrations of phosphate in the Baltic Sea Area, 2003

Note: Coastal stations are marked by circles and ICES open-water stations (>20 km from coast) by squares

Data source:

Waterbase (data from OSPAR, HELCOM and EEA member countries compiled by ETC Water).

Downloads and more info

Mean winter surface concentrations of nitrate+nitrite in the Black Sea, 2003

Note: Coastal stations are marked by circles and ICES open-water stations (>20 km from coast) by squares

Data source:

Waterbase (data from OSPAR, HELCOM and EEA member countries compiled by ETC Water).

Downloads and more info

Mean winter surface concentrations of nitrate+nitrite in the Mediterranean Sea, 2003

Note: Coastal stations are marked by circles and ICES open-water stations (>20 km from coast) by squares

Data source:

Waterbase (data from OSPAR, HELCOM and EEA member countries compiled by ETC Water).

Downloads and more info

Mean winter surface concentrations of nitrate+nitrite in the Greater North Sea, the Celtic Seas and the Northeast Atlantic, 2003

Note: Coastal stations are marked by circles and ICES open-water stations (>20 km from coast) by squares

Data source:

Waterbase (data from OSPAR, HELCOM and EEA member countries compiled by ETC Water).

Downloads and more info

Mean winter surface concentrations of nitrate+nitrite in the Baltic Sea Area, 2003

Note: Coastal stations are marked by circles and ICES open-water stations (>20 km from coast) by squares

Data source:

Waterbase (data from OSPAR, HELCOM and EEA member countries compiled by ETC Water).

Downloads and more info

Mean winter surface nitrate/phosphate-ratio in the Black Sea, 2003

Note: Coastal stations are marked by circles and ICES open-water stations (>20 km from coast) by squares

Data source:

Waterbase (data from OSPAR, HELCOM and EEA member countries compiled by ETC Water).

Downloads and more info

Mean winter surface nitrate/phosphate-ratio in the Mediterranean Sea, 2003

Note: Coastal stations are marked by circles and ICES open-water stations (>20 km from coast) by squares

Data source:

Waterbase (data from OSPAR, HELCOM and EEA member countries compiled by ETC Water).

Downloads and more info

Mean winter surface nitrate/phosphate-ratio in the Greater North Sea, the Celtic Seas and the Northeast Atlantic, 2003

Note: Coastal stations are marked by circles and ICES open-water stations (>20 km from coast) by squares

Data source:

Waterbase (data from OSPAR, HELCOM and EEA member countries compiled by ETC Water).

Downloads and more info

Mean winter surface nitrate/phosphate-ratio in the Baltic Sea Area, 2003

Note: Coastal stations are marked by circles and ICES open-water stations (>20 km from coast) by squares

Data source:

Waterbase (data from OSPAR, HELCOM and EEA member countries compiled by ETC Water).

Downloads and more info

Mean winter surface concentrations of phosphate in the Black Sea, 2003

Note: Coastal stations are marked by circles and ICES open-water stations (>20 km from coast) by squares

Data source:

Waterbase (data from OSPAR, HELCOM and EEA member countries compiled by ETC Water).

Downloads and more info

Mean winter surface concentrations of phosphate in the Mediterranean Sea, 2003

Note: Coastal stations are marked by circles and ICES open-water stations (>20 km from coast) by squares

Data source:

Waterbase (data from OSPAR, HELCOM and EEA member countries compiled by ETC Water).

Downloads and more info

Key assessment

Nitrate

In the OSPAR (the North Sea, the English Channel and the Celtic Seas) and HELCOM (the Baltic Sea bounded by the parallel of the Skaw in the Skagerrak at 57o44.8'N) areas the available time-series show no clear trend in winter surface concentrations of nitrate. Both decreasing and increasing trends are observed at 3-4 % of the stations (Figure 1) which is certainly attributable to the temporal variability of nutrient loads resulting from varying run-offs.

In the Baltic Sea, winter surface nitrate concentrations are low, even in many coastal waters (the background concentration in the open Baltic Proper is around 65 microgram/l (EEA 2001)). The higher concentrations observed in the Belt Sea and the Kattegat are due mainly to the mixing of Baltic waters with the more nutrient-rich North Sea and Skagerrak waters. The enhanced concentrations resulting from local loading are particularly noticeable in the coastal waters of Lithuania, the Gulf of Riga, the Gulf of Finland, the Gulf of Gdansk, the Pommeranian Bay and Swedish estuaries (Figure 2).

In the OSPAR area the nitrate concentrations are high (>600 microgram/l) due to land-based loads into the coastal waters of Belgium, the Netherlands, Germany, Denmark, and in a few UK and Irish estuaries (Figure 13). Background concentrations in the open North Sea and Irish Sea are about 129 microgram/l and 149 microgram/l, respectively (EEA 2001). In the Dutch coastal waters, an overall decrease of 10-20% in winter nitrate concentrations has been observed, when normalising the concentration to salinity and using a smoothing trend detection method. Denmark reported significant decreasing trends in the annual mean concentrations of nitrate+nitrite+ammonium, both in coastal waters and in the open Kattegat and Belt Sea.

In the Mediterranean Sea, nitrate concentrations have increased at 24 % and decreased at 5 % of the Italian coastal stations (Figure 1). The background concentration is low, i.e. only 7 microgram/l. Relatively low concentrations are observed in the Greek coastal waters, around Sardinia and the Calabrian Peninsula. Slightly higher concentrations are observed along the  north-west and south-east Italian coasts. High concentrations are observed in most of the northern and western Adriatic Sea, as well as close to rivers and cities along the Italian west coast.

In the Black Sea, the background concentration of nitrate is very low, i.e. 1.4 microgram/l (Figure 11). A slight decrease in nitrate concentration has been reported in the Romanian coastal waters, with a steady decline in the Turkish waters at the entrance to the Bosphorus (Black Sea Commission 2002). An increased level of both nitrate and phosphate in Ukrainian waters during recent years is connected to high river run-offs (Black Sea Commission 2002).

Phosphate

In the Baltic and North Seas, phosphate concentrations have decreased at 25 % and 33 % of the coastal stations, respectively (Figure 1). In the Greater North Sea, the decline in phosphate concentrations is especially evident in the Dutch and Belgian coastal waters, which is probably due to reduced phosphate loads  from the river Rhine. Decreases in phosphate concentrations have also been observed at some stations in the German, Norwegian and Swedish coastal waters, and in the open North Sea (more than 20 km from the coast). In the Baltic Sea area, decreases in phosphate concentrations were observed in the coastal waters of most countries, except Poland, as well as in the open waters.

In the Baltic Sea area (Figure 10), the winter surface phosphate concentration is very low in the Bothnian Bay compared with the background concentrations in the open Baltic Proper, and is potentially limiting primary production in the area. The concentration is slightly higher in the Gulf of Riga, the Gulf of Gdansk, in some Lithuanian, German and Danish coastal waters and in estuaries. Remedial measures have been taken in the catchment areas and a reduction in the use of fertilisers has occurred. However, recent research indicates that phosphate concentrations, for example in the open Baltic waters including the Kattegat, are strongly influenced by processes and transport within the water body due to variable oxygen regimes in the bottom water layer (Rasmussen et al. 2003). The phosphate concentration is exceptionally high in the Gulf of Finland due to hypoxia and the up-welling of phosphate-rich bottom water in the late 1990s (HELCOM 2001).

In the North Sea, the English Channel and the Celtic Seas, phosphate concentrations in the coastal waters of Belgium, the Netherlands, Germany and Denmark are elevated compared to those of the open North Sea. The concentrations in the estuaries are generally high due to local loads (Figure 9).

In the Mediterranean Sea, phosphate concentrations have increased at 26 % and decreased at 8 % of the Italian coastal stations (Figure 1). Concentrations higher than the background value (i.e. about 1 microgram/l) are observed in most coastal waters, and much higher concentrations are observed in hot spots along the  east and west coasts of Italy (Figure 8).

In the open Black Sea, the background phosphate concentration is relatively high (about 9 microgram/l) compared with the Mediterranean Sea and the background nitrogen value. This is probably due to the permanently anoxic conditions in the bottom waters of most of the Black Sea, which prevent the phosphate from being bound in the sediments. The phosphate concentration along the Turkish coast is lower than in the open sea, while it is higher in the Romanian coastal waters influenced by the Danube River (Figure 7). In the Black Sea, a slow decline in the concentrations of phosphate has been reported in the Turkish waters at the entrance to the Bosphorus (Black Sea Commission 2002).

N/P Ratio

In the Baltic Sea, the N/P ratio, based on winter surface nitrate and phosphate concentrations, is increasing in all areas (Figure 1) except the Polish coastal waters. The N/P ratio is high (>32) in the Bothnian Bay, where it is likely that phosphorus limits the  primary production of phytoplankton. However, the N/P ratio is low (<8) to relatively low (<16) in most of the open and coastal Baltic Sea area, indicating that nitrogen can be a potential growth-limiting factor (Figure 6).

In the Greater North Sea and Celtic Seas, high N/P ratios (>16) are observed in the Belgian, Dutch, German and Danish coastal waters and estuaries (Figure 5), indicating potential phosphorus limitation, at least early in the growing season. In more open waters, the N/P ratio is generally below 16, indicating potential nitrogen limitation.

In the Mediterranean Sea, high N/P ratios (>32) are found along the northern Adriatic coast and at hot spots along the Italian coasts and the north coast of Sardinia (Figure 4), indicating potential phosphorus limitation, at least during some periods of the growing season.

In the Black Sea, the N/P ratio is generally low, especially in the open sea and along the Turkish coast, indicating potential nitrogen limitation. High N/P ratios (>32) are  found only at a few Romanian coastal stations (Figure 3), indicating potential phosphorus limitation.

Data sources

More information about this indicator

See this indicator specification for more details.

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EEA Contact Info

Constança De Carvalho Belchior

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EEA Management Plan

2005 1.4.2 (note: EEA internal system)

Dates

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Updates are scheduled every 1 year in July-September (Q3)
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